/*

 MinIMU-9-Arduino-AHRS
 Pololu MinIMU-9 + Arduino AHRS (Attitude and Heading Reference System)

 Copyright (c) 2011 Pololu Corporation.
 http://www.pololu.com/

 MinIMU-9-Arduino-AHRS is based on sf9domahrs by Doug Weibel and Jose Julio:
 http://code.google.com/p/sf9domahrs/

 sf9domahrs is based on ArduIMU v1.5 by Jordi Munoz and William Premerlani, Jose
 Julio and Doug Weibel:
 http://code.google.com/p/ardu-imu/

 MinIMU-9-Arduino-AHRS is free software: you can redistribute it and/or modify it
 under the terms of the GNU Lesser General Public License as published by the
 Free Software Foundation, either version 3 of the License, or (at your option)
 any later version.

 MinIMU-9-Arduino-AHRS is distributed in the hope that it will be useful, but
 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
 more details.

 You should have received a copy of the GNU Lesser General Public License along
 with MinIMU-9-Arduino-AHRS. If not, see <http://www.gnu.org/licenses/>.

 */

#include <math.h>

//#include <pololu/orangutan.h>

#include "MinIMU9AHRS.h"

void Compass_Heading()
{
	float MAG_X;
	float MAG_Y;
	float cos_roll;
	float sin_roll;
	float cos_pitch;
	float sin_pitch;

	cos_roll = cos(roll);
	sin_roll = sin(roll);
	cos_pitch = cos(pitch);
	sin_pitch = sin(pitch);

	// adjust for LSM303 compass axis offsets/sensitivity differences by scaling to +/-0.5 range
	c_magnetom_x = (float) (magnetom_x - SENSOR_SIGN[6] * M_X_MIN) / (M_X_MAX
			- M_X_MIN) - SENSOR_SIGN[6] * 0.5;
	c_magnetom_y = (float) (magnetom_y - SENSOR_SIGN[7] * M_Y_MIN) / (M_Y_MAX
			- M_Y_MIN) - SENSOR_SIGN[7] * 0.5;
	c_magnetom_z = (float) (magnetom_z - SENSOR_SIGN[8] * M_Z_MIN) / (M_Z_MAX
			- M_Z_MIN) - SENSOR_SIGN[8] * 0.5;

	// Tilt compensated Magnetic filed X:
	MAG_X = c_magnetom_x * cos_pitch + c_magnetom_y * sin_roll * sin_pitch
			+ c_magnetom_z * cos_roll * sin_pitch;
	// Tilt compensated Magnetic filed Y:
	MAG_Y = c_magnetom_y * cos_roll - c_magnetom_z * sin_roll;
	// Magnetic Heading
	MAG_Heading = atan2(-MAG_Y, MAG_X);
}
